1. Field of the Invention
This invention relates in general to air conditioning devices and more particularly to an air conditioning apparatus which operates on the principal of evaporative cooling.
2. Description of the Prior Art
Devices for cooling air by the evaporation principal have been used for many years with the most successful use of such devices being in relatively dry climates for both commercial and residential applications.
The most common evaporative cooler in use today includes a cabinet in which an air moving device, usually in the form of a motor driven centrifugal blower, is mounted for drawing ambient air into the cabinet through wettable pads mounted in the sides thereof. As the relatively dry ambient air moves through the wet pads, it is cooled by evaporation and the air moving device delivers the cooled air to an outlet that is normally located in the bottom of the cabinet. A sump located in the bottom of the cooler cabinet is provided with a float valve which maintains a predetermined water level in the sump, and a motor driven pump is employed to supply water under pressure from the sump into a distribution plumbing network mounted in the top of the cabinet. The water is delivered to the tops of the pads by the plumbing network and flows under the influence of gravity through the pads with the unevaporated water returning to the sump for recirculation.
Although evaporative coolers of the above described type are recognized as low cost and relatively efficient devices, there are several problems associated with the use, operation, maintenance, and deterioration of such devices.
The wettable pads mounted in the sides of the cooler cabinet provide resistance to the inflow of ambient air into the cabinet. A certain amount of this resistance is taken into consideration by designing the cooler with an air moving device of a larger size than would be needed in the absence of this resistance. The oversized air moving device is higher in initial and operating costs, however, the real problem is encountered by contamination buildup in the pads. Since evaporation occurs within and proximate the pads, calcification or mineral deposition, along with airborne dirt and other foreign matter will collect in the pads thus increasing the resistance to airflow therethrough. The pads commonly used are loosely packed excelsior wrapped in a relatively large mesh fabric such as cheesecloth. It is not practical to clean such pads thus, periodic replacement is required. In view of this, it will be seen that the operating efficiency and operating costs will steadily become worse as the cooler is used, and will become a serious problem if the period between pad replacement is excessively long, or if replacement is ignored entirely as is all too often the case.
Other problems with the wettable pads used in the prior art evaporative coolers include channelization of the water trickling through the pads, improperly packed excelsior which results in dry spots and uneven airflow through the pads, and the pads are a fire hazard when they are dry.
The moisture laden air emerging from the cooler pads into the interior of the cabinet will deposit some of the entrained moisture on every surface and operating component in the cabinet. For this reason, the interior cabinet surfaces, motor mounts, air moving structure, and the like within the cabinet are galvanized or otherwise provided with rustproofing coatings to minimize the corrosive effect of the moisture. The most serious problem resulting from this moisture entrainment is that it is deposited on the electric wiring, connections, and on the motors which operate the air moving device and the pump, and actually enters into the motors themselves through the air circulation ports thereof and is deposited on the motor windings. Such mineral deposition on the electric components causes a general deterioration of the wiring and the motors and in time, which can be quite short in areas of highly mineralized water, will cause shorting out of the motors. This general deterioration of the electric components coupled with the above mentioned highly flammable state of cooler pads when they are dry results in a serious fire hazard and due to the close proximity of water and wet components when the coolers are operating, a high electric shock potential is present.
Another problem with these prior art evaporative coolers is the relatively high occurrence rate of flooding damage brought on by the float controlled water inlet valves which malfunction due to contaminants in the water and cause the sumps to overflow.
Another type of evaporative cooler was suggested in U.S. Pat. No. 1,951,962 issued to F. G. Baum on Mar. 20, 1934. In this evaporative cooler, a motor is axially mounted in a duct casing with the motor having an output shaft which extends from opposite ends thereof. A first fan driven by the motor is located at the outlet of the casing and is operated to draw air through the casing and thereby create a zone of reduced air pressure therein. A second fan on the other end of the motor has an enlarged hub with tubes extending radially therefrom and having spray nozzles on the ends of those tubes. A third fan is gear driven off of the hub of the second fan and includes a revolving dipper mechanism for supplying water from a sump to the radial tubes of the second fan. The three fans induce a swirling airflow through the casing and the rotating tubes centrifugally deliver water to the spray nozzles which spray that water into the air movement path through the duct casing. This cooler did not achieve any appreciable degree of commercial success to the best of our knowledge due to its costs, complexity, and due to all of its operating components being located within the duct casing where they are subject to corrosion and mineral deposition.
Other devices have been devised in which the cooling of air by evaporation inherently occurs as a result of the principal objectives of those devices. Those devices, which are exemplified in U.S. Pat. Nos. 2,709,578 and 3,406,498, have the primary objectives of humidification and the washing of air or gas, and all have the same basic problems of costs, complexity and component damage due to corrosion and mineral deposition, and relatively high electric shock and fire hazard potential.
Therefore, a need exists for a new and improved evaporative cooler which overcomes some of the problems and shortcomings of the prior art.